The present invention relates to an electronic drive system for droplet spray generation and, more particularly to an electronic drive system for use in a droplet spay generator for an air-freshening device.
An aim of the present invention is to provide a low cost electronic drive system for a droplet generator using a micro-controller to implement signal generation and timing elements of a circuit to drive the droplet generator.
Spray generators of the general type to which the present invention relates may, for example, be of the type described in EP-A-0615470.
WO-A-2005/097348 describes an electronic drive system for a droplet spray generation device of the type having a droplet generator including a perforate membrane driven by a piezoelectric transducer, the electronic drive system comprising a programmable micro-controller, a power supply for converting, in use, a battery supply voltage to power the device, a power amplifier connected to receive electric power from the power supply and supply a drive signal to the piezoelectric generator in use; and wherein the micro-controller is also arranged to control the operation of the power amplifier, including the drive signal operating frequency at substantially its resonant frequency, to measure the current provided to the power amplifier by the power supply at a plurality of different frequencies, to determine, as the resonant frequency of the droplet generator, the frequency at which the maximum power is consumed by the amplifier, and to set the drive signal operating frequency at the resonant frequency. Such a system effectively therefore determines the resonant frequency to use based on current measurement.